Blown-fuse indicator including a circuit-controlling switching device

ABSTRACT

A unit including an indicating fuse and a switching device under the control of said indicating fuse is designed to be more compact and easier to manufacture than comparable prior art devices. This is achieved by providing a tubular member of insulating material mounted on one of the terminal caps of an indicating fuse, covering but one portion of the particular cap, and exposing another portion thereof, said tubular member of insulating material forming a support for a switching device which includes relatively movable contact means.

United States Patent [72] Inventor Paul C. Hltchcock,Sr. 3,179,774 4/ I965 Swain 337/244 I-Iaverhlll, Mass. 2,794,095 5/l957 Kozocka 337/5 X I 1 pp 887,504 FOREIGN PATENTS Sig 32; 1,165,722 10/1969 Great Britain 337/186 s Assignee The Chmshawmut Company 1,560,404 2/1969 France 337/244 Newburyport, Mass. Primary Examiner-Remard A. Gilheany Assistant Examiner- Dewitt M. Morgan Attorney-Erwin Salzer [54] BLOWN-FUSE INDICATOR INCLUDING A CIRCUIT-CONTROLLING SWITCHING DEVICE 7 Claims, 4 Drawing Flgs.

[52] US. Cl. 337/5, ABSTRACT; A unit induding an indicating f and 3 337/244 switching device under the control of said indicating fuse is [5 Int. Cl. de igned to be more compact and easier to manufacture than OSfll'ch 6, 7, om arable prior an devices is achieved providing 3 I42, I43, I45, I47, I48, I86, I90, I94, I97, I98, tubular member of insulating material mounted on one of the 206, 208, 209, 1 244; 200/153 T terminal caps of an indicating fuse, covering but one portion of the particular cap, and exposing another portion thereof, [56] References CM said tubular member of insulating material forming a support UNITED STATES PATENTS for a switching device which includes relatively movable con- 3,450,949 6/I969 Inglis 337/7 X tact means.

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mvenrom PAUL C. HITCHCOCK BY MAMA/m ATTY.

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BLOWN-FUSE INDICATOR INCLUDING A CIRCUIT- CONTROLLING SWITCHING DEVICE BACKGROUND OF THE INVENTION Many power fuses include a blown-fuse indicator to indicate whether or not the power fuse has blown. There are many instances where it is desired to structurally separate the blownfuse indicating means form the power fuse. In such instances an indicating fuse separate from the power fuse is shunted across the power fuse. The former includes a spring-biased indicator pin, or striker pin, normally maintained against its spring bias in a given position by means of a restraining wire. Upon blowing of the power fuse a voltage appears across the terminals of the indicating fuse and the ensuing current causes fusion of the restraining wire. Hence the indicator pin, or striker pin, is shifted under the action of its spring bias from its initial position to another position, i.e., its indicating or operating position. In many instances it is necessary to translate the aforementioned motion of the indicator pin, or striker pin, into a contact-closing motion, or into a contact-separating motion. This calls for a combination including an indicating fuse and a switching device. Units including an indicating fuse and a switching device must often be used in large numbers at places where there are most stringent space limitations, e.g., in large silicon rectifier systems. This calls for indicator fuse and switching device units of great compactness.

SUMMARY OF INVENTION BRIEF DESCRIPTION OF DRAWINGS FIG. I is substantially a vertical section of a unit embodying this invention including an indicating fuse and a switching device operatively related to the latter, some of the parts of the unit being shown in elevation rather than in section;

FIG. 2 is a section along Il-ll of FIG. 1;

FIG. 3 is a side elevation of a portion of the structure of FIG. I seen in the directionof the arrow R of FIG. 1; and

FIG. 4 showsa modification of the structure of FIG. 1, partly in vertical section and partly in side elevation.

DESCRIPT OF PREFERRED EMBODIMENTS In FIGS. 1-3 reference character I has been applied to generally designate an indicating fuse. The particular indicating fuse shown in FIG. 1 is of the type disclosed and claimed in US. Pat. No. 3,l79,774 to Kenneth W. Swain, Apr. 20, 1965 for INDICATING AND ACT UATING FUSES. Another type of indicating and actuating fuses may be substituted for the fuse I of FIGS. 1-3. In FIGS. 1 and 3 reference character S has been applied to generally designate a switching device operatively related to fuse I, and reference character T has been applied to generally indicate tie means integrating parts I and S to fonn a self-sustained structural unit. The indicating fuse I of FIG. 1 includes a casing 1 of insulating material closed both ends by ferrules or terminal caps 2. Restraining wire 3 is arranged inside of casing l and extends along the axis thereof. The inside of casing l is filled with a pulverulent arcquenching tiller 4 surrounding restraining wire 3. Each ferrule or terminal cap 2 has a perforation in the center thereof and restraining wire 3 is threaded through the perforations in parts 2. The upper end of restraining wire 3 is threaded through a rubber seal 5 and through the lower opening provided in a pin ing pin 7. Pin support 6 has an upper opening receiving operating pin 7, and the latter is press fitted into that opening. Thus the upper end of restraining wire 3 is firmly attached to unit 6,7. The latter is biased in upward direction by helical compression spring 8. The lower end. of spring 8 rests against the upper ferrule or tenninal-cap 2. An eyelet 9 inserted into the center perforation of lower ferrule or terminal cap 2 forms a bushing for the passage of restraining wire 3 from the inside of casing 11 tothe outside-thereof. Eyelet 9 and the convex end surface of lower ferrule or terminal, cap 2 are filled. with soft solder, thus affixing the lower end of wire 3 to the lower ferrule or terminal cap 2. An outer terminal cap 10a is mounted onthe lower ferrule or terminal cap 2, and the lower end of wire 3 is clamped between the lateral. surfaces of the first-mentioned andthe last-mentioned terminal cap. An outer terminal cap 10b ismounted on the upper ferrule or terminal cap 2 and defines a chamber 11 housing seal 5, pin support 6 and helical pin-biasing spring 8. Terminal cap 10b has a central aperture for the passage of operating pin 7. The switching device S includes a housing 12 of insulating material which is preferably formed by a molded piece of a synthetic resin defining a switching chamber 13. Four tenninal lugs 14 project from the outside of housing 12 through the sidewalls of the latter into switching chamber 13. The ends of terminal lugs 14 inside of switching chamber 13' support fixed contacts 15. Operating member 16 of electric insulating material is arranged above, and in coaxial relation to, operating pin 7 and slidably guided in a conforming aperture formed in the lower wall of switch housing 12. The movable contact support 17 integral with operating member 16 is arranged above the latter and acted upon by helical compression spring 18. Compression spring 18 biases parts 16 and 17 in downward direction. Reference character 19 has been applied to indicate two contact arms whose outer ends support double-faced contact buttons 20 and whose inner ends engage knife bearings formed by contact support 17. Helical spring 21 extends between two points of contact arms 19 relatively remote from contact support 17. Screw studs 22 project through housing 12 and secure an angle member 23to the former. Angle member 23 includes a horizontal flange defining a pair of coaxial circular sleeves 230,235 leaving a toroidal gap therebetween. A tubular member 24 of electric insulating material is press fitted with its upper edge portion into the toroidal gap formed between parts 23a and 23b, and is thus firmly secured to angle member 23 and consequently also to switch housing 12. Member 24 is frictionally mounted on the upper tenninal cap 10b of indicating fuse I. Member 24 covers one portion, i.e., the upper portion, of the lateral surface of the upper terminal cap 10b and exposes another portion, i.e., the lower portion, of the lateral surface of the upper terminal cap 10b. The exposed or lower portion of the lateral surface of upper terminal cap 101: is engaged by fuse holder clip 25b. The lateral surface of lower terminal cap 10a is engaged by fuse holder clip 25a. Fuse holder clips 25a,25b are electrically connected across a power fuse (not shown). As long as the power fuse is intact its fusible means fonn a low-resistance shunt across fuse holder clips 254,251). Hence no voltage prevails between fuse holder clips 25a,25b. Upon blowing of the power fuse a voltage appears across fuse holder clips 25a,25b. Hence a current flows from clip 25a, through caps 10a, 2, restraining wire 3, pin support 6, spring 8 and caps 2,101; to clip 25b. This current causes melting of restraining wire 3, thus forming a break between its ends, as shown in FIG. 1. Hence spring 8 tends to propel parts 16 mounted on casing I and 17 in upward direction against the action of relative weak compression spring 18.

Prior to fusion of restraining wire 3 parts 16,17 are in their.

lower limit position, spring 18 is expanded and movable contacts 20 engage the upper fixed contacts 15. When parts 7,16,17 are moved in upward direction under the bias of helical spring 8 and the knife bearings of contact arms 19 are moved beyond the dead center position relative to spring 21, the double-face contact buttons 20 snap out of engagement with the upper fixed contact 15 and into engagement with the support 6 and wedged between pin support 6 and the operatlower fixed contacts 15.

Fuse I is a device that must be replaced following each blowing, but switch 8 is a device capable of performing a very large number of switching operations and calls hardly for any replacement. Upon blowing of fuse I it is simply pulled out of tubular insulating member 24 and replaced by a like fuse which is intact.

The switch S shown is a SPDT switch of the type called twocircuit switch. It is designed to normally maintain one circuit closed and another circuit open. Upon blowing of fuse I the nonnally closed circuit is opened, and the normally open circuit is closed. This is a requirement which often occurs in supervisory systems for electric fuses. The switch 5 is a snap-action-type device capable of performing a very large number of switching operations under relatively onerous conditions. There are, however, many supervisory systems for electric fuses requiring a relatively small number of switching operations under conditions which are not onerous. In such instances the greatly simplified structure of FIG. 4 may be preferable over that of FIGS. 1-3.

In FIG. 4 the same reference characters as in FIGS. 1-3 with a prime added have been applied to designate like parts. Thus I is an indicating fuse identical to that shown in FIG. 1 and described in connection with FIG. I. This fuse includes an upper tenninal cap b and an operating pin 7'. The tubular member 24' of insulating material is frictionally mounted on terminal cap 10b. Tubular member 24' covers the upper portion of terminal cap 10b and exposes the lower portion of cap 10b in order to make it possible to place fuse I in a pair of fuse holder clips (not shown) as explained above in connection with FIG. 1. The operating member 16' of insulating material is arranged inside tubular member 24 in coaxial relation to member 24' and operating pin 7'. Helical compression spring 18' rests with one end thereof against a shoulder formed by tubular member 24' and with the other end thereof against operating member 16'. The upper portion of tubular member 24' defines a switching chamber 13 and lugs 14' project transversely through member 24' into switching chamber I3. Tubular member 24 is closed on the upper end thereof by a cover 26'. The inner ends of lugs 14' form contact surfaces 15'. The operating member 16' of insulating material supports the movable contact support 17' which, in turn, supports the contact bridge 19. Contact bridge 19' is adapted to conductively interconnect selectively either the upper lugs 14' or the lower lugs 14'.

While FIG. 1 shows the fuse I following blowing thereof, FIG. 3 shows fuse I' prior to blowing thereof. Upon blowing of fuse 1' its pin 7 is propelled upwardly under the action of its pin-biasing spring overcoming the bias of compression spring I8. Consequently contact bridge 19' is moved out of engagement with lower lugs 14' and into engagement with upper lugs I4.

It will be apparent that in the switch structure of FIG. 4 the current path between the upper lugs 14' is normally open and the current path between the lower lugs 14' closed, while in the structure of FIG. I the current path between upper lugs 14 is normally closed and the current path between lower lugs 14 normally open. Normally means in this context prior to energizing and blowing of the fuse by which the respective switching device is controlled.

The tubular member 24 of FIGS. 1-3 and the tubular member 24' of FIG. 4 are preferably made of nylon. They may also be made of an elastomer. In the latter instance the inner diameter of members 24 and 24', respectively, ought to be smaller than the outer diameter of upper terminal caps 10b and 10b, respectively. Members 24,24 expand when mounted on caps l0b,l0b.

I claim as my invention:

l. A blown-fuse indicator and electric switch unit including a. a tubular casing of insulating material, a fusible restraining wire housed in said casing, a spring-biased indicator pin arranged adjacent one of the ends of said casing and normally restrained by said restraining wire, and a pair of terminal caps mounted on the axially outer ends of said casing and nonnally conductively interconnected by said restraining wire;

b. a circuit-controlling switching device arranged adjacent said one of the ends of said casing and adjacent said indicator pin and operable by said indicator pin, said switching device including a pair of contacts for closing and opening an electric circuit; and

c. a tubular member of insulating material frictionally mounted on one of said pair of terminal caps, said member of insulating material covering one portion of the lateral surface of one of said pair of tenninal caps and exposing another portion of the lateral surface of said one of said pair of terminal caps, and said member of insulating material supporting said switching device and said pair of contacts thereof.

2. A blown-fuse indicator as specified in claim 1 wherein the lateral surface of said member of insulating material is shorter than said lateral surface of said one of said pair of tenninal caps and exposes the axially inner end of said lateral surface of said one of said pair of tenninal caps.

3. A blown-fuse indicator as specified in claim 2 wherein said member of insulating material consists of an elastomer.

4. A blown-fuse indicator as specified in claim I wherein said member of insulating material is in the form of an additional cap and wherein said pair of contacts is arranged inside said additional cap and wherein terminal means for said pair of contacts are arranged on the lateral surface of said additional cap.

5. A blown-fuse indicator as specified in claim I wherein said tubular member of insulating material consists of nylon.

6. A blown-fuse indicator as specified in claim 3 wherein said tubular member of insulating material has a smaller inner diameter than the outer diameter of said one of said pair of terminal caps.

7. A blown fuse indicator and electric switch unit including a. a tubular casing of insulating material, a fusible restraining wire housed in said casing, a spring-biased indicator pin arranged adjacent one of the ends of said casing and normally restrained by said restraining wire, and a pair of terminal caps mounted on the axially outer ends of said casing and normally conductively interconnected by said restraining wire;

b. a circuit-controlling switching device arranged adjacent said indicator pin and adjacent one of said pair of terminal caps and operable by said indicator pin, said switching device including fixed contacts and movable contacts;

c. a tubular member of insulating material frictionally mounted on said one of said pair of terminal caps, said member of insulating material covering one portion of the lateral surface of said one of said pair of terminal caps and exposing another portion of the lateral surface of said one of said pair of terminal caps, and said member of insulating material supporting parts of said switching device including the fixed contacts thereof; and a pair of contact clips, one of said pair of contact clips engaging the portion of the lateral surface of said one of said pair of terminal caps exposed by said tubular member, and the other of said pair of contact clips engaging the other of said pair of tenninal caps.

i k l i 

1. A blown-fuse indicator and electric switch unit including a. a tubular casing of insulating material, a fusible restraining wire housed in said casing, a spring-biased indicator pin arranged adjacent one of the ends of said casing and normally restrained by said restraining wire, and a pair of terminal caps mounted on the axially outer ends of said casing and normally conductively interconnected by said restraining wire; b. a circuit-controlling switching device arranged adjacent said one of the ends of said casing and adjacent said indicator pin and operable by said indicator pin, said switching device including a pair of contacts for closing and opening an electric circuit; and c. a tubular member of insulating material frictionally mounted on one of said pair of terminal caps, said member of insulating material covering one portion of the lateral surface of one of said pair of terminal caps and exposing another portion of the lateral surface of said one of said pair of terminal caps, and said member of insulating material supporting said switching device and said pair of contacts thereof.
 2. A blown-fuse indicator as specified in claim 1 wherein the lateral surface of said member of insulating material is shorter than said lateral surface of said one of said pair of terminal caps and exposes the axially inner end of said lateral surface of said one of said pair of terminal caps.
 3. A blown-fuse indicator as specified in claim 2 wherein said member of insulating material consists of an elastomer.
 4. A blown-fuse indicator as specified in claim 1 wherein said member of insulating material is in the form of an additional cap and wherein said pair of contacts is arranged inside said additional cap and wherein terminal means for said pair of contacts are arranged on the lateral surface of said additional cap.
 5. A blown-fuse indicator as specified in claim 1 wherein said tubular member of insulating material consists of nylon.
 6. A blown-fuse indicator as specified in claim 3 wherein said tubular member of insulating material has a smaller inner diametEr than the outer diameter of said one of said pair of terminal caps.
 7. A blown fuse indicator and electric switch unit including a. a tubular casing of insulating material, a fusible restraining wire housed in said casing, a spring-biased indicator pin arranged adjacent one of the ends of said casing and normally restrained by said restraining wire, and a pair of terminal caps mounted on the axially outer ends of said casing and normally conductively interconnected by said restraining wire; b. a circuit-controlling switching device arranged adjacent said indicator pin and adjacent one of said pair of terminal caps and operable by said indicator pin, said switching device including fixed contacts and movable contacts; c. a tubular member of insulating material frictionally mounted on said one of said pair of terminal caps, said member of insulating material covering one portion of the lateral surface of said one of said pair of terminal caps and exposing another portion of the lateral surface of said one of said pair of terminal caps, and said member of insulating material supporting parts of said switching device including the fixed contacts thereof; and d. a pair of contact clips, one of said pair of contact clips engaging the portion of the lateral surface of said one of said pair of terminal caps exposed by said tubular member, and the other of said pair of contact clips engaging the other of said pair of terminal caps. 